Industrial burners fired with liquid fuels employ nozzles which atomize the liquid fuel before or as the fuel is discharged from the nozzle into a combustion chamber or the like. Typically, steam but sometimes compressed air or another compressed gas is combined with the liquid fuel so that the fuel is atomized into minute droplets suspended in the atomizing steam or gas. The atomized fuel is then discharged from the nozzle, ignited and combusted.
In some instances it is necessary to combust liquid fuels which are difficult to ignite. Such fuels may either represent a relatively inexpensive source of energy, e.g. a lower quality fuel, or they may constitute waste that needs to be incinerated. Frequently it is difficult to combust such fuels because they have relatively few volatiles that can be driven off at relatively low temperatures and which can then be ignited to raise the temperature of the remainder of the fuel to its combustion temperature. To effectively incinerate heavy fuels it is, therefore, necessary to discharge them into a combustion zone or chamber which has the requisite temperature. One such approach involves the provision of multiple burners, some of which are fired with conventional fuel oil, for example, to raise the temperature of the combustion zone while other burners discharge into the zone the waste fuel.
U.S. Pat. No. 3,414,198 discloses such an arrangement in which, within an industrial boiler, for example, some of the burners are fired with liquid waste fuels or the like having a relatively low heat value while other burners are fired with relatively high heat value fuels, e.g. with fuel oil. This patent further discloses to construct the burners so that they can be operated with either of the two fuels by replacing appropriate portions of the burners. The arrangement appears to be well suited for large installations, such as industrial boilers or steam generators in which relatively large amounts of heat must be generated. In such instances, the combustion chamber is relatively large and well heated and the waste fuels can be combusted therein without significant problems by appropriately atomizing them and discharging them into the chamber where the waste fuel droplets are quickly and adequately heated to sustain their combustion.
In installations in which much less heat is to be generated, or in instances where the primary concern is the incineration of waste fuels to circumvent problems that are encountered if such fuels are otherwise disposed of, the arrangement disclosed in the above-referenced patent is impractical because it would be necessary to construct a relatively large combustion chamber which must be uniformly heated to the temperature required to ignite the waste fuel. If the required temperatures are not reached the combustion of the waste fuel will be incomplete and fuel particles will be discharged as highly objectionable pollutants. Thus, there is presently a need for an efficient and preferably inexpensive device which permits the atomization and combustion of waste fuels and the like by heating such fuels to the required temperature with a minimum amount of the much more expensive primary fuel.